1. Field of the Invention
The present invention relates to a pressure sensitive switch used mainly for operating various electronic devices and an input device using the pressure sensitive switch.
2. Description of the Related Art
Recently, in accordance with improved functions and diversification of various electronic devices such as cellular phones and car navigation devices, pressure sensitive switches used in such operations and input devices using the pressure sensitive switches require a high operation speed and easiness for use.
Such conventional pressure sensitive switches and input devices using the pressure sensitive switch will be described with reference to FIGS. 20 to 22. For easy understanding of the configuration thereof, in the diagrams, the size in the thickness direction is represented with being enlarged.
FIG. 20 is a cross-sectional view of a conventional pressure sensitive switch, and FIG. 21 is an exploded perspective view of the conventional pressure sensitive switch. In FIGS. 20 and 21, movable contact point 2 having an approximate dome shape is bonded to the lower face of film-shaped cover sheet 1 by using an adhesive agent (not shown).
Movable contact point 2 can be bonded to five places of an approximate center position on film-shape base sheet 3 having flexibility, which is the same as that of cover sheet 1, and the front, rear, left, and right sides thereof by cover sheet 1.
Movable contact assembly 6 is configured by cover sheet 1, movable contact point 2, base sheet 3, sheet resistive body 4 located on the lower face thereof, and insulating layer 5 disposed in an area acquired by excluding a portion that becomes the center on the lower side of movable contact point 2.
On the upper and lower faces of substrate 7 having a film shape or a plate shape, a plurality of wiring patterns (not shown) are formed with copper foil or the like. In five places of an approximate center position of substrate 7 and positions located on the front, rear, left, and right side thereof, fixed contact point pair 8 is formed. Fixed contact point pair 8 is formed by opposing fixed contact points 8A and 8B having a half circle shape with a predetermined gap interposed therebetween.
On the upper side of each fixed contact point pair 8, movable contact assembly 6 is placed so as to face a portion of sheet resistive body 4 that is not covered with insulating layer 5 through a predetermined gap, whereby the pressure sensitive switch is configured.
In addition, on the upper face of substrate 7, electronic circuit 12 that is configured by constant voltage power supply 9, resistor 10, control unit 11, and the like is disposed. Constant voltage power supply 9 is connected to fixed contact point 8A. Control unit 11 is connected to fixed contact point 8B. Resistor 10 has one end connected to fixed contact point 8B and the other end connected to the ground. The input device is configured as described above. Control unit 11 is configured by a microcomputer or the like.
On the upper side of movable contact assembly 6, rubber sheet 13 formed from insulating resin, pressure button 14 formed from insulating resin, and operation body 15 formed from insulating resin are disposed. Rubber sheet 13 has a plurality of pressing portions 13A on the lower face thereof, and pressing portions 13A are brought into contact with the upper face of cover sheet 1 located in the center portion of the plurality of movable contact points 2. On the upper side of pressing portions 13A, pressure button 14 is disposed so as to be movable in the vertical direction, and operation body 15 is disposed so as to be able to rock.
In the above-described configuration, for example, when the pressure button 14 located at the center is pressed in the downward direction, the center of rubber sheet 13 is bent so as to press movable contact point 2 located on the lower side thereof. At that time, movable contact point 2 is elastically inverted in the downward direction with the sense of clicking given to the user. Accordingly, sheet resistive body 4 is bent in the downward direction, and the lower face of sheet resistive body 4 is brought into contact with fixed contact points 8A and 8B, whereby fixed contact points 8A and 8B are electrically connected to each other through sheet resistive body 4.
Thereafter, when the pressing force is further applied, sheet resistive body 4 is further bent in accordance with the pressing force. Accordingly, contact areas between the sheet resistive body 4 and fixed contact points 8A and 8B are increased, and thereby a resistance value between fixed contact points 8A and 8B decreases.
In addition, when operation body 15 is rocked by pressing the front, rear, left, and right sides of operation body 15, movable contact point 2 located on the lower side of the pressing position is elastically inverted in the downward direction with the sense of clicking incurred, similarly to the case of pressing the pressure button 14 located at the center. Accordingly, sheet resistive body 4 is bent in the downward direction, and the lower face of sheet resistive body 4 is brought into contact with fixed contact points 8A and 8B located on the lower side of each pressing position. Therefore, fixed contact points 8A and 8B are electrically connected to each other through sheet resistive body 4.
Then, when the pressing force is further applied, sheet resistive body 4 is further bent in accordance with the pressing force. Thus, the contact areas between sheet resistive body 4 and fixed contact points 8A and 8B are increased, and the resistance value between fixed contact points 8A and 8B decreases, which is the same as the case of pressing pressure button 14 located at the center.
The change in the resistance value is detected by control unit 11 of electronic circuit 12 that is formed on the upper face of substrate 7 through constant voltage power supply 9 and resistor 10 as a change in the voltage. Based on the change in the voltage, for example, as shown in the perspective view of an electronic device of FIG. 22, the movement direction or movement speed of pointer 19 used for selecting a plurality of menus 18 displayed in display means 17 of cellular phone 16 are controlled by control unit 11.
In other words, when position A located on the right side of operation body 15 is pressed, control unit 11 controls pointer 19 to move to the right side in accordance with the pressing operation. On the other hand, when position B located on the left side is pressed, control unit 11 controls pointer 19 to move to the left side in accordance with the pressing operation. In addition, when the pressing force applied to operation body 15 is strong, control unit 11 controls pointer 19 to move at a higher speed.
As a related art relating to the present invention, for example, Japanese Patent Unexamined Publication No. 2009-016330 is known.
However, in the above-described conventional pressure sensitive switch and the input device using the pressure sensitive switch, for example, in order to reversely move the cursor, which has been moved in the rightward direction, in the leftward direction, the finger pressing the right end portion of operation body 15 needs to be departed once and press the left end portion thereof. Accordingly, the pressing position of operation body 15 needs to be checked by moving the operator's eyes off the screen once. Therefore, there is a problem in that a smooth operation is disturbed.